Our objective is to advance innovative cardiorenal protective peptide therapeutics for heart failure (HF) with a special focus on the post-acute HF period, which is a high-risk phase of HF for rehospitalization and increased mortality. Our therapeutic target is the natriuretic peptide/particulate guanylyl cyclase-A receptor/cGMP (NP/pGC-A/cGMP) and Angiotensin1-7/Mas (ANG1-7/Mas) receptor pathways. Both possess cardiorenal protective and anti-renin-angiotensin-aldosterone system (RAAS) properties. An overriding theme is that optimal HF therapeutics must be multivalent promoting the NP/cGMP system while opposing RAAS. This theme is underscored by our hypothesis of an intrarenal imbalance between the NP/pGC-A/cGMP and RAAS pathways in human post-acute HF. Our proposal builds on our expertise in developing innovative designer NPs. HL36634 supported the development of CD-NP (Cenderitide), a dual pGC-A/pGC-B activator, which received an IND and is in clinical trials for HF. Here we advance NPA7, our newest generation designer peptide, which may represent a truly superior therapeutic for HF. NPA7 is a first-in-class multivalent peptide with dual receptor activating actions. NPA7, unlike CD-NP or native NPs, co-targets the cardiorenal protective pGC-A and Mas receptors for which ANP/BNP and ANG1-7 are endogenous ligands respectively. We hypothesize that NPA7 amplifies the cardiorenal protective properties via these two complementary pathways. We also hypothesize that NPA7 will have synergistic actions which go beyond pGC-A or Mas receptor activation alone. Preliminary studies in experimental HF reveal cardiorenal activation of deleterious molecular pathways of inflammation, apoptosis, and fibrosis. We hypothesize that such pathway activation may, in part, be linked to excessive cardiorenal angiotensin II (ANG II) and a relative deficiency of NP/cGMP, especially in the kidney, leading to detrimental cardiorenal structural changes and dysfunction, which is also supported by preliminary studies in experimental HF. This imbalance we hypothesize characterizes human post-acute HF. Indeed, defining this imbalance is important especially in the kidney in the setting of human post-acute HF in which there is insufficient knowledge of intrarenal RAAS and NP/cGMP pathway activity, and could support the rationale for co-targeting of the NP/cGMP and RAAS pathways with NPA7. The impact of our application is high, addressing the need for new drugs for post-acute HF for which there are no FDA approved therapies. Completion of our aims will advance innovation in the area of multivalent receptor activation, and move NPA7 to the IND ready level for clinical trials in post-acute HF. Our Specific Aims are as follows: Aim 1: Determine pGC-A and Mas receptor binding of NPA7 in HEK293 cells selectively overexpressing human pGC- A or Mas receptors together with defining cardiorenal protective properties of NPA7 in human renal tubular cells, cardiomyocytes and renal and myocardial fibroblasts. Aim 2: Determine the cardiorenal protective properties and RAAS inhibiting actions of chronic NPA7 therapy in a large animal model of HF, which mimics post-acute HF. Aim 3: Determine urinary and circulating components of the NP/cGMP system and RAAS in human post-acute HF with a special focus on an intrarenal NP/cGMP and RAAS imbalance.